The A,B,Gs of silencing

摘要

Transcriptional silencing of mammalian genes is mediated by at least two modes of methylation: (1) cytosine methylation of DNA, and (2) methylation of the his tones tails梑oth of which play an important role in transcriptional silencing from chromosomal DNA. Although there is some evidence that these pathways are interdependent, experimentally, they have largely been treated as two distinct processes. In this issue of Genes & Development, Smallwood et al. (2007) have taken a pioneering step toward defining the molecular mechanism by which these two types of methylations can cooperate to silence a euchromatic gene, and demonstrate that the DNA methyltransferase 1 (DNMT1) cytosine methyl -transferase physically and functionally interacts with three Heterochromatin Protein 1 (HP1) family members (a,beta,and gamma) to implement gene silencing#